Nutrition plays a critical role in maintaining and restoring good health. When the body faces disease or physiological stress, proper nutrition plays an increasingly important role.
The characterization and marketing of naturally and non-naturally occurring antioxidants is receiving widespread attention in the everyday lives of many people today. Certain food groups having high levels of antioxidants are believed to provide prophylactic health benefits. Therefore, a myriad of supplements, herbal formulations, and herbal extracts are being marketed to consumers. In many cases, these compositions are promoted without solid scientific foundation. Currently, there is increased scientific interest in the role of antioxidants and the part they play in human health by reducing excessive free radicals.
There are two distinct mechanisms for cell death. Apoptosis is the result of “normal” or programmed cell death. Through this physiological process cells are routinely eliminated, giving balance to the proliferation of new cells. During apoptosis the outer membrane of the cell forms “bubbles” known as blebs. The content of the cells becomes incased in the blebs. The blebs separate from the cell and are digested by nearby cells or macrophages. This orderly process greatly reduces toxicity to surrounding cells.
Necrosis is the other form of cell death. This is not a programmed event and is known as “accidental” death. This pathological process occurs when cells are exposed to extreme stress, chemical insult, and resultant free radical damage. The early stages of necrosis involve a swelling of the cell called oncosis. During oncosis the cell and its organelles begin to swell due to an exchange in the cell's potassium to sodium ratios. Necrosis, after the oncosis stage, is an explosive event where the cells contents stream directly into the surrounding cells environment causing damage and an immune response. Controlling necrosis during the early oncosis stage is important. Up to this point, necrosis is a reversible event. The morphology of cells dying by necrosis centers on changes in the cell's permeability. Hengartner M O, The biochemistry of apoptosis. Nature 407: 770-776, 2000. Osmotic changes take place during an exchange of cytosol potassium and extracellular sodium. Early stage necrosis, known as oncosis, is characterized by the dilation or swelling of the cell and its organelles due to this exchange. Cell survival of this non-programmed event is dependent upon repairing the cell's membrane and stopping the flow of sodium ions into the cells interior. Repair of the cell's membrane and improvement in the cell's environment to more homeostatic conditions are paramount to survival
Quiescence is the counterpart to proliferation and is a normal part of the cell cycle. The cell's replicative cycle involves a myriad of molecular events that occur during the quiescent state (G0) and trigger the progression to the prereplicative (G1) phase. Cosenza S C, Owen T A, Soprano D R, Soprano K J, Evidence That the Time of Entry into S is Determined by Events Occurring in Early G1. J Biological Chem 263; 12751-12758; 1988. The G0 phase represents not just the absence of signals for mitosis but an active repression of the genes needed for mitosis. This is an important distinction since cancer cells cannot enter G0 and as a consequence become immortal.
During quiescence, a cell will reduce in size yet remain dynamic and metabolically active. A quiescent cell is more notable for what it does not do such as synthesize DNA. Coller H A, Sang L, Roberts J M, A New Description of Cellular Quiescence. PLos Biology. 4:0329-0349.2006. Quiescent cells are in a “state-of-readiness,” like hibernation, waiting for the appropriate signal that it is once more time to move to the G1 phase. Cells have a built-in conservation mechanism allowing it to survive for extended periods. Gray J V, Petsko G A, Johnston C, Ringe D, Singer R A, Werner-Washburne M, “Sleeping Beauty”: in Saccharomyces cerevisiae. Microbiology and Molecular Biology Reviews. 68:2; 187-206:2004. If the cell remains in the quiescence state for an extended period, however, its ability to proliferate diminishes. Stated differently, the longer a cell stays in abnormal quiescence the more likely it becomes that the cell will die via necrosis. Just as with early stage necrosis, however, early quiescence is a reversible event that can be corrected by changing the cell's environment and reduction of free radicals in the cell's environment appears to be critical to the reversal process. See, e.g., Coller H A, Sang L, Roberts J M, 2006 A New Description of Cellular Quiescence. PLoS Biol 4(3): e83. doi:10.1371/journal.pbio.0040083.